PURPOSE: The c1q assay has been proposed as a potential adjunct to standard donor specific antibody (DSA) testing designed to improve the specificity to identify pathologic antibodies. However, data on its effectiveness has been inconsistent. We sought to evaluate its use in a cohort of kidney and kidney/pancreas transplant patients for prediction of both clinical and serologic outcomes.

METHODS: We retrospectively analyzed data for all patients who developed de novo DSA since our current screening program began in January 2012. Average follow-up time was 18 months. Antibodies were reported by mean fluorescence intensity (MFI) and the lowest titer at which they could be identified. C1q was categorized as negative or as positive with a graded 6 point scale based on the MFI of the c1q assay. Statistical calculations were made using Fisher's exact test with a two tailed P value.

RESULTS: C1q negative patients were not found to be statistically more likely to reach the serologic endpoints of reduction or elimination of DSA, or the clinical endpoints of long term renal impairment or graft loss (see table 1). While c1q approached statistical significance for a reduction in antibody, we also found that c1q negativity was very highly associated (p=0.0001) with lower titers of antibody, and that the titer of antibody was a stronger predictor of the studied endpoints.

CONCLUSION: C1q assays do not seem to add to the information available from standard assays regarding graft survival, renal function, or antibody resolution. A positive c1q result is highly associated with higher titers of antibody, and it may be the latter that truly provides the best information regarding the danger posed by de novo DSA.

CITATION INFORMATION: Gilbert A, Zaheer M, Timofeeva O, Awwad M, Li D, Rosen-Bronson S, Javaid B, Grafals M, Verbesey J, Abrams P, Cooper M. C1q Assays Are Not Associated with Clinical or Serologic Endpoints. Am J Transplant. 2016;16 (suppl 3).

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